This invention is related to a method for winding web material such as tissue paper or paper toweling into individual logs. More particularly, the invention is related to a method for controlling winding of a web on a turret winder.
Turret winders are well known in the art. Conventional turret winders comprise a rotating turret assembly which supports a plurality of mandrels for rotation about a turret axis. The mandrels travel in a circular path at a fixed distance from the turret axis. The mandrels engage hollow cores upon which a paper web can be wound. Typically, the paper web is unwound from a parent roll in a continuous fashion, and the turret winder rewinds the paper web onto the cores supported on the mandrels to provide individual, relatively small diameter logs.
While conventional turret winders may provide for winding of the web material on mandrels as the mandrels are carried about the axis of a turret assembly, rotation of the turret assembly is indexed in a stop and start manner to provide for core loading and log unloading while the mandrels are stationary. Turret winders are disclosed in the following U.S. Pat. No.: 2,769,600 issued Nov. 6, 1956 to Kwitek et al; U.S. Pat. No. 3,179,348 issued Sep. 17, 1962 to Nystrand et al.; U.S. Pat. No. 3,552,670 issued Jun. 12, 1968 to Herman; and U.S. Pat. No. 4,687,153 issued Aug. 18, 1987 to McNeil. Indexing turret assemblies are commercially available on Series 150, 200, and 250 rewinders manufactured by the Paper Converting Machine Company of Green Bay, Wis.
The Paper Converting Machine Company Pushbutton Grade Change 250 Series Rewinder Training Manual discloses a web winding system having five servo controlled axes. The axes are odd metered winding, even metered winding, coreload conveyor, roll strip conveyor, and turret indexing. Product changes, such as sheet count per log, are said to be made by the operator via a terminal interface. The system is said to eliminate the mechanical cams, count change gears or pulley and conveyor sprockets.
Various constructions for core holders, including mandrel locking mechanisms for securing a core to a mandrel, are known in the art. U.S. Pat. No. 4,635,871 issued Jan. 13, 1987 to Johnson et al. discloses a rewinder mandrel having pivoting core locking lugs. U.S. Pat. No. 4,033,521 issued Jul. 5, 1977 to Dee discloses a rubber or other resilient expansible sleeve which can be expanded by compressed air so that projections grip a core on which a web is wound. Other mandrel and core holder constructions are shown in U.S. Pat. Nos. 3,459,388; 4,230,286; and 4,174,077.
Indexing of the turret assembly is undesirable because of the resulting inertia forces and vibration caused by accelerating and decelerating a rotating turret assembly. In addition, it is desirable to speed up converting operations, such as rewinding, especially where rewinding is a bottleneck in the converting operation.
Accordingly, it is an object of the present invention to provide an improved method for controlling winding of a web material onto individual hollow cores.
Another object of the present invention is to provide a method of continuously rotating a turret assembly, and of phasing the rotational position of a turret winder with that of a position reference.
Another object of the present invention is to reduce the position errors of a plurality of individually driven components, including a turret assembly, a core loading component, and a core stripping component, while driving the components.
The present invention comprises a method of controlling winding of a continuous web of material into individual logs. In one embodiment, the method comprises the steps of: providing a rotatably driven turret assembly supporting a plurality of rotatably driven mandrels for winding the logs; providing a rotatably driven bedroll for providing transfer of the continuous web of material to the rotatably driven turret assembly; rotating the bedroll; rotating the rotatably driven turret assembly, wherein rotation of the turret assembly is mechanically decoupled from rotation of the bedroll; determining the actual position of the turret assembly; determining a desired position of the rotatably driven turret assembly; determining a turret assembly position error as a function of the actual and desired positions of the turret assembly; and reducing the position error of the turret assembly while rotating the rotatably driven turret assembly.
The steps of determining the desired and actual positions of the rotatably driven turret assembly can comprise the steps of: providing a position reference while rotating the turret assembly; determining the desired position of the rotatably driven turret assembly relative to the position reference while rotating the turret assembly; and determining the actual position of the turret assembly relative to the position reference while rotating the turret assembly.
The position reference can be calculated as a function of the angular position of the bedroll. In one embodiment, the position reference is calculated as a function of the angular position of the bedroll, and as a function of an accumulated number of revolutions of the bedroll. For instance, the position reference can be calculated as the position of the bedroll within a log wind cycle.
The step of rotating the rotatably driven turret assembly can comprise the step of continuously rotating the turret assembly after the step of reducing the position error of the turret assembly is completed. For instance, the step of rotating the turret assembly can comprise the step of rotating the turret assembly at a generally constant angular velocity after the step of reducing the position error of the turret assembly is completed.
In one embodiment, the method of the present invention comprises the steps of: providing at least two independently driven components, the position of each independently driven component being mechanically decoupled from the positions of the other independently driven components, wherein at least one of the independently driven components comprises a rotatably driven turret assembly supporting a plurality of rotatably driven mandrels for winding the logs; driving each of the independently driven components; providing a common position reference; determining the actual position of each independently driven component relative to the common position reference while driving the independently driven component; determining the desired position of each independently driven component relative to the common position reference while driving the independently driven component; determining a position error for each independently driven component as a function of the actual and desired positions of the independently driven component; and reducing the position error of each independently driven component while driving the component. The step of providing at least two independently driven components can comprise the steps of providing an independently driven component for loading a core onto each of the mandrels and providing an independently driven component for removing wound logs from the mandrels.